Disinfection of areas of medical facilities is a key component to reduce or eliminate hospital acquired infections, also known in the art as nosocomial diseases or infections. The problem has become so serious that many medical facilities close or restrict areas to allow for intensive methods to eradicate the micro-organisms that cause these infections.
Germicidal radiation including ultraviolet radiation and more recently high intensity narrow spectrum (HINS) light have been found to be ways to treat these areas to reduce the levels of these micro-organisms. Ultraviolet germicidal irradiation is a disinfection method that uses ultraviolet radiation at a sufficiently short wavelength to break down these micro-organisms. Ultraviolet-C radiation with a wavelength of between 180-280 nm (and particularly between 240 nm-280 nm) has been found to be particularly effective. UV-B between 280-320 nm also has germicidal properties. The relatively short wavelengths of ultraviolet-C and B radiation are harmful to forms of life at the micro-organic level by destroying the ability of microorganisms to reproduce by causing photochemical changes in nucleic acids in these organisms so that their DNA and/or RNA chemical structure is disrupted. The disruption prevents micro-organisms from replicating, thereby rendering them inactive and unable to cause infection.
Disinfecting using ultraviolet radiation has been limited. This is mainly due to existing systems being configured to require the treated areas to be unoccupied by people. This precaution stems from the fact that UV exposure to unprotected skin can produce various negative effects including erythema, photosensitivity, skin aging, immune system damage, and even increased occurrences of skin cancer. The most serious effects of UV exposure are those which affect the eyes, the results of which can produce photokeratitis and conjunctivitis and other corneal injuries, including potentially cataracts in the eye lens. It so happens that the wavelengths most effective for germicidal uses are also the wavelengths that are most destructive to human tissue. Thus, these existing systems cannot be used in areas populated by people who are not properly protected from UV radiation. Or when used, their application is limited to relatively small physical areas such as unoccupied rooms, floors, ductwork, doorways, or ceilings or inside of air purifying devices and the like. Since the 1930's the use of UV radiation during surgeries has occasionally been practiced, but in these instances personnel in the area are fully protected from the UV with clothing, skin creams, and UV protective eyewear which is administratively controlled for the short duration of the surgery. More recently, UV radiation devices are being used to irradiate rooms in hospitals after patients are discharged or after surgeries are completed, so called “terminal cleaning,” and studies are showing that when rooms are treated by UV radiation in this way that infection rates of subsequent occupants of the rooms are lowered. In all cases in the application of such germicidal radiation devices, persons are required to leave the room or environment to avoid being irradiated with harmful UV radiation. Overall, UV radiation systems are not conducive to treating areas in which people are routinely located, thus limiting the major benefits they can provide. UV radiation, with proper protection, can be superior to other forms of sanitation which are used to reduce microorganism populations, such as periodic cleanings with bleach or emitting a toxic chemical mist into the air. Being able to continuously irradiate an environment with germicidal radiation would have the most benefits. But the inability to ensure administratively that everyone in an area is properly protected at all times and for extended periods of time makes the continuous or semi-continuous use of UV decontamination in the presence of persons infeasible.
More recently, other wavelengths of radiation in the visible range have been found to have germicidal activity. High intensity narrow spectrum light (HINS) in the range of 380 to 420 nm, violet light, and particularly the 400-410 nm range centered on 405 nm, has been found to have some germicidal activity. Although these wavelengths are not harmful to humans as is UV radiation, because such high intensities are needed it would not be desirable to expose the unprotected human eyes to HINS.
Being able to expose environments to germicidal radiation without allowing the germicidal radiation to contact persons in the environment, or exposing the environment and persons in the environment to germicidal radiation after first electronically confirming that the persons in the environment are adequately protected from the germicidal radiation, is currently unknown. All known germicidal decontamination systems either go to great lengths to ensure that persons are not present in the environment when the radiation is emitted or assume that administrative procedures have been followed and are adequate to ensure that the person is fully protected.